/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.dex.code.form;

import java.util.BitSet;

import com.android.dx.dex.code.CstInsn;
import com.android.dx.dex.code.DalvInsn;
import com.android.dx.dex.code.InsnFormat;
import com.android.dx.rop.code.RegisterSpecList;
import com.android.dx.rop.cst.Constant;
import com.android.dx.rop.cst.CstLiteralBits;
import com.android.dx.util.AnnotatedOutput;

/**
 * Instruction format {@code 22b}. See the instruction format spec for details.
 */
public final class Form22b extends InsnFormat {

	/** {@code non-null;} unique instance of this class */
	public static final InsnFormat THE_ONE = new Form22b();

	/**
	 * Constructs an instance. This class is not publicly instantiable. Use
	 * {@link #THE_ONE}.
	 */
	private Form22b() {
		// This space intentionally left blank.
	}

	/** {@inheritDoc} */
	@Override
	public String insnArgString(DalvInsn insn) {
		RegisterSpecList regs = insn.getRegisters();
		CstLiteralBits value = (CstLiteralBits) ((CstInsn) insn).getConstant();

		return regs.get(0).regString() + ", " + regs.get(1).regString() + ", "
				+ literalBitsString(value);
	}

	/** {@inheritDoc} */
	@Override
	public String insnCommentString(DalvInsn insn, boolean noteIndices) {
		CstLiteralBits value = (CstLiteralBits) ((CstInsn) insn).getConstant();
		return literalBitsComment(value, 8);
	}

	/** {@inheritDoc} */
	@Override
	public int codeSize() {
		return 2;
	}

	/** {@inheritDoc} */
	@Override
	public boolean isCompatible(DalvInsn insn) {
		RegisterSpecList regs = insn.getRegisters();
		if (!((insn instanceof CstInsn) && (regs.size() == 2)
				&& unsignedFitsInByte(regs.get(0).getReg()) && unsignedFitsInByte(regs
				.get(1).getReg()))) {
			return false;
		}

		CstInsn ci = (CstInsn) insn;
		Constant cst = ci.getConstant();

		if (!(cst instanceof CstLiteralBits)) {
			return false;
		}

		CstLiteralBits cb = (CstLiteralBits) cst;

		return cb.fitsInInt() && signedFitsInByte(cb.getIntBits());
	}

	/** {@inheritDoc} */
	@Override
	public BitSet compatibleRegs(DalvInsn insn) {
		RegisterSpecList regs = insn.getRegisters();
		BitSet bits = new BitSet(2);

		bits.set(0, unsignedFitsInByte(regs.get(0).getReg()));
		bits.set(1, unsignedFitsInByte(regs.get(1).getReg()));
		return bits;
	}

	/** {@inheritDoc} */
	@Override
	public void writeTo(AnnotatedOutput out, DalvInsn insn) {
		RegisterSpecList regs = insn.getRegisters();
		int value = ((CstLiteralBits) ((CstInsn) insn).getConstant())
				.getIntBits();

		write(out, opcodeUnit(insn, regs.get(0).getReg()),
				codeUnit(regs.get(1).getReg(), value & 0xff));
	}
}
